Tri-phase PZT-porous polyurethane (PU) composites are investigated with the aim of developing conformable, highly sensitive tactile sensors for application in Human-Machine Interactions. The main goal is to reduce the dielectric constant of the polymer matrix, and improve flexibility of traditional diphase piezo-composites, consisting of ceramic particles in a dense polymeric matrix, by adding a third (gaseous) phase to the system. The presence of the gaseous component in the polymer matrix in the form of well-distributed spherical inclusions effectively decreases the polymer dielectric permittivity, which improves the piezoelectric voltage coefficient of the composites significantly. The unique combination of dielectrophoretic structuring of PZT particles and the addition of a gaseous phase to the polymer resin results in the highest performance of the particulate composite sensors reported in the literature so far. The g33 values of the newly developed triphase composites are twice that of the structured di-phase PZT-dense PU composites (80 mV.m/N) and more than five times the g33 value of bulk PZT ceramics (24-28 mV.m/N).